Hydraulically enhanced well drilling technique

ABSTRACT

A method for drilling a well bore hole using a drill string which includes an extensible hydraulic cylinder and piston section located above the drill bit. The drill string is positioned such that the extensible section is in less than a fully extended condition while pressurized fluid is pumped into the extensible section to produce hydraulic forces tending to extend that section. The hydraulic force thus generated within the extensible section influences the effective drill string weight applied to the drill bit and thus controls the force actually exerted between the drill bit and the bottom of the bore hole.

United States Patent [191 Varley June 11, 1974 IIYDRAULICALLY ENHANCED WELL DRILLING TECHNIQUE [22] Filed: Oct. 20, 1972 [21] Appl. No.: 299,235

[52] US. Cl. 175/65, 175/321 [51] Int. Cl E21b 3/00 [58] Field of Search 175/57, 6|, 65, 321

[56] References Cited UNITED STATES PATENTS 2.ll3,65l 4/l938 Heaston l75/32l 3,088,532 5/1963 Kellner l75/32l X FOREIGN PATENTS OR APPLICATIONS Primary Examiner-ALfred R. Guest Attorney, Agent, or Firm-Cushman, .Darby & Cushman [5 7] ABSTRACT A method for drilling a well bore hole using a drill string which includes an extensible hydraulic cylinder and piston section located above the drill bit. The drill string is positioned such that the extensible section is in less than a fully extended condition while pressurized fluid is pumped into the extensible section to produce hydraulic forces tending to extend that. section. .The hydraulic force thus generated within the extensible section influences the effective drill string weight applied to the drill bit and thus controls the force actually exerted between the drill bit and the bottom of the bore hole.

Germany 175/321 9 Claims, 1 a ng Figure 172/42 M/g: j 2m. V'Ef/(RL Fem sin/v JE/VE WE 16/17- Alf/4N5 AVE/4122 1a J LIP/01 51115 550w HYDRAULICALLY ENHANCED WELL DRILLING TECHNIQUE This invention generally relates to the drilling of well bore holes such as in the drilling of oil wells. More spe-- cifically, it relates to a method for drilling such holes by utilizing hydraulic forces in an extensible section of the drill string to control the force with which the drill bit is urged against the bottom of a bore hole during a drilling operation.

In my prior US. Pat. No. 3,599,733 issued Aug. 17, 1971, I have described a method for enhanced directional jet drilling utilizing a reciprocatable in-hole mud pump located relatively adjacent to a directional jetting bit in the drill string. In essence, this in-hole mud pump comprises an extensible cylinder and piston section having a back pressure operated fluid valve at the top thereof. In the technique described in my prior patent, this extensible section is first fully extended to fill the cylinder with-mud after which the drill string is lowered thus trapping the cylinder full of mud behind the back pressure valve, thereafter compressing the mud and forcing it out of the jet drilling bit at an increased velocity.

It has now been discovered that basically this same drill string structure may be utilized in other methods for even further'enhancing either directional jet drilling, drilling out, angle building, straight forward and- /or other drilling operations.

In the past, the effective force with which the drill bit is forced against the bottom of a bore hole has been controlled to some extent by controlling the portion of the drill string weight which is supported by the drilling rig. That is, by slacking off some of the supporting force, more drill string weight is permitted to act in forcing the drill bit against the bottom of the bore hole. Conversely, by increasing the lifting force on the drill string, less force (from the drill string weight) is effectively transmitted to the drilling bit.

However, this technique of controlling the force on the drilling bit is less than perfect especially when long lengths of drill pipe or drill string, significant frictional forces, etc., are involved. Furthermore, when performing offshore drilling on a floating rig, normal vertical wave motion of the rig makes it virtually impossible .to maintain the desired force between the drill bit and the bottom of the drill bore hole. This problem is generally recognized and one attempted solution involving the use of multiple bumper subs and drill collars is described in Turbodrilling from Floating Rigs" by L.

Dicky, Petroleum Engineer, June, 1972.

The hydraulically enhanced drilling operations encompassed within the newly discovered method of this invention represents a substantial improvement over past techniques of controlling the force between the drill bit and the bottom of a bore hole.

ln the method of this invention, the drill string is constructed to include an extensible hydraulic cylinder and piston section located above a drill bit in a manner similar to that disclosed in my prior US. Pat. No. 3,599,733; However, the drill bit positioned at the bottom of the drill string in this invention may comprise any kind of conventional jetting and/or other drilling bit..The extensiblesection is-positioned in a partially retracted or less than fully extended position such that substantially the whole force urging the drill bit against the bottom of the bore hole comprises the hydraulic force generated within the extensible hydraulic cylinder and piston section when pressurized fluid is admitted into that section. That is, pressurized fluid exerts a force against the piston tending to extend the extensible section and force the drill bit against the bottom of the bore hole with exactly this amount of force. Accordingly, by controlling the hydraulic fluid pressure and hence the'hydraulic force exerted upon the piston of said extensible section, the force with which the drill bit is urged against the bottom of the bore hole may be accurately controlled.

In particular, so long as the hydraulic fluid pressure is maintained substantially constant (and possible frictional side effects are minimized by rotating drill string), the force with which the drill bit is urged against the bottom of the bore hole will also remain substantially constant so long as the extensible section is somewhere within the extremes of its normal travel. That is, so long as the extensible section is not fully extended or fully retracted, the force with which the drill bit is urged against the bottom of the bore hole will be substantially determined by the pressurized fluid pressure acting to produce hydraulic forces within the extensible cylinder and piston section of the drill string. Accordingly, so long as the available travel in the extensible section is of sufficient magnitude, even the wave motion of floating drilling rigs will not substantially alter the force with which the drill bit is urged against the bottom of a bore hole. Furthermore, even in straight forward drilling operations, a substantially constant drill bit force may be obtained by periodically repositioning the drill string to insure that the extensible section is always somewhere between the two'extremes or limits of travel.

These and other objects of the invention will be more fully explained in the following detailed description and in the accompanying drawing which schematically depicts an exemplary drill string and bore hole as it might appear in practicing this invention.

As shown in the drawing, the drill string 10 is normally connected to a Kelly bar 12 which passes through a rotary drive mechanism 14. The drill string is suspended from a drilling rig 16 through a vertical drive means 18 and usually attached to some form of -drill string weight indicator 20. Pressurized mud is pumped into the drill string at 22 as will-be appreciated by those in the art.v While the drilling rig 16 has been shown as fixed in the drawing, it should be appreciated that the drilling rig may in fact be on a floating platform in offshore operations and therefore not necessarily fixed with respect to the bore hole 24.

In simplistic terms, for purposes of explanation, the drill string 10 may be thought of as a weight suspended by the vertical drive means 18. If an absolute slack is permitted in suspension line 26, then the drill string weight indicator 20 would indicate the weight of the drill string minus the upward force 28 (if any) exerted by the bottom of the bore hole on the drill bit 30 as shown in the drawing. Accordingly, if the drill bit 30 is not yet in contact with the bottom of the bore hole, the drill string weight indicator would indicate the total weight of the drill string. On the other hand, if the drill bit is in contact with the bottom of the bore hole and the vertical drive means 18 completely slacks off suspension line 26, the entire weight of the drill string would be'supported by the force 28ithus causing the drill string weight indicator 20 to indicate zero.

As shown in the drawing, near the lower end of the drill string 10, an extensible section 32 is included just above the drill bit 30. A back pressure valve 34 may be included for in-hole mud pumping operations as explained in my prior US. Pat. No. 3,599,733. The extensible section 32 comprises a cylinder portion 36 and a piston portion 38. As shown in the drawing, the extensible section 32 is slightly more than half-way extended with the piston 38 being somewhere between the fully retracted position 40 and a fully extended position 42 as should now be apparent. The piston 38 is connected with a mandrel 44 to which the drill bit 30 is attached at the bottom end thereof. A fluid conduit 46 permits pressurized fluid entering the cylinder 36 to also pass through the conduit 46 into jetting and/or lubricating conduits as shown schematically in the drill bit 30. A hex drive sub 48 cooperates with the outside hexagonal shape of the mandrel 44 to transmit rotary motion to the bit 30 if such rotary motion is imparted to the drill string through rotary drive means 14 as will be appreciated by those in the art.

Accordingly, when mud is pumped into the cylinder 36, the piston 38 will be forced downwardly to extend the extensible section 32 if the total force on the face of the piston 38 from the mud pressure (hydraulic) is greater than the opposing upward force 28 exerted on the face of the bit.

For enhanced jet directional drilling as described in my prior US. Pat. No. 3,599,733, the drill bit 30 would, of course, be a directionaltype of jetting bit and, after desired orientation of this bit, the tool would be operated by raising the drill string sufficiently to permit the extensible section 32 to fully extend. At this point, the piston or cylinder chamber 36 would be filled with mud. The drill string would then be quickly slacked off and lowered until the bit touches the bottom, the back pressure valve would then close thus permitting the travelling weight of the drill string to force the extensible section 32 into its retracted position and thus force the mud out through the passage 46 and the jet directional bit 30 at a velocity which is much greater than the normal velocity which can be attained by surface mud pumps alone. This reciprocating procedure is then repeated according to my previous invention until a pocket has been formed to result in a desired angle or change of angle in the drilled bore hole.

It has now been discovered that even after the jet directional operation according to my previous patent has been completed, the extensible section 32 may be left at the end of the drill string to further enhance a drilling out" operation. During the drilling out operation, the drill bit is rotated while simultaneously lowering the bit 30 to drill a new section of the bore hole at the new angle. In this operation, after the directional jetting operation has been completed, the tool is left closed with the bit 30 located at the bottom of the bore hole. Mud pressure is then held down to permit this closing of the extensible section or tool 32. The actual weight or fore 28 on-the bit face is then adjusted as desired by raising or lowering the drill string from the rig 4, and rotation of the drill string and bit is begun for the drilling out process.

Thereafter, the mud pressure is again increased. This hydraulic pressure tends to extend the piston and cylinder or extensible section 32, which extension can only result in one of two things happening. Namely, the drill string will either be lifted or the mandrel 42 with the attached bit 30 will begin to drop which is, of course, equivalent to a successful drilling out operation. By maintaining a constant mud pressure, the force on the bit will thus remain constant until the tool is finally fully extended, if friction effects are disregarded. The process just described can be cyclically repeated after the tool is again closed by momentarily reducing mud pressure and slacking off on the vertical drive means as should now be apparent.

For instance, in a typical example, the weight of an entire string might be indicated as 200,000 pounds when the bit is on the bottom of the bore hole and the tool or extensible section 32 is half closed. With the pump started, the drill string is put into rotation to make sure that it is completely free within the bore hole. As the pump pressure is increased, the weight indication on the floor shows 165,000 pounds, a decrease of some 35,000 pounds. Of course, this decrease in weight is directly attributable to the upward force 28 acting at the bottom of the string which is, in turn, caused by the hydraulic action of the extensible section 32. That is, the 35,000 pound decrease on the weight indicator 20 means that the bit is in fact loaded by a force of 35,000 pounds.

This result can perhaps be better understood by mentally envisioning a set of spring scales from which a 10 pound weight is suspended. Now further envision a hydraulic cylinder extending between the floor and the bottom of the 10 pound weight. When no fluid pressure is supplied to the hydraulic cylinder, the scale will read the full 10 pounds, However, when sufficient pressure is applied to the hydraulic cylinder to lift 5 pounds of the weight, the scale will read 5 pounds instead of 10. As should now be appreciated, if the change in opposing upward force at the bottom of the hydraulic cylinder were to be measured, it would exactly equal the weight loss of 5 pounds as indicated on the scales.

This usage of the extensible section 32 for drilling out after directional jetting operations greatly enhances the process of changing the angle of the drilled bore hole because of the constant bit pressure as well as because of the greater flexibility of the hexagonal mandrel 24 as compared to a standard drill pipe or collar due to its smaller outside diameter and dimensional tolerances resulting in natural play or motion between the hex drive 48 and the mandrel 44 as the tool is extended. This flexibility allows a greater degree of angle change or deviation to be accomplished than if the tool were left closed or not used at all. r

ln soft formations, the drilling out procedure may still be performed with the tool fully retracted if desired since all the advantages accruing from the use as stated above might not beneeded. However, in medium formations, the advantages of the above discussed method will begin to becomeimportant. Here, the bit should be pulled free of the bottom and then the drill string slacked off slowly until the bit touches the bottom and the tool is closed at least partially. At this point, thepressure on, the string should be rotated slowly and drilled into the pocket with the tool fully extended. After the bit has broken free the drill string should be slacked off fast enough to partially close the tool after which it should be further slacked off slowly to the bottom until the tool is fully retracted (adding the drilling weight to the indicator) before the drilling process as described above is continued.

In exceedingly hard or deep formations, it may become necessary to jet four or five times on a single joint in order to turn a hole as desired. In this type of jetting and drilling, it is essential that the rotary table and rotary bushings be correctly marked and that all makeup is out of the drill pipe and that the drilling torque be worked out of the drill string before jetting in order to stay correctly oriented. v

in ordinary drilling situations where angle building problems have been encountered, the tool described above will build angle at the rate of l% to 2 per 100 feet. in exceedingly difficult situations or where the rate of build required exceeds the ordinary building rate, the following procedure has been found to be advantageous.

The drilling bit should be placed on the bottom of the bore hole. With full mud pump pressure, the drill string should be rotated while the tool is closed at least partially. Then, with the rotary motion temporarily stopped, the tool should be closed completely as indicated by the added drill collar weight on the weight indicator. Then, the rotating motion should be started again but without slacking off on the vertical drive. That is, the upper portion of the drill string down to and including the cylinder 40 is effectively suspended or held in a position just indicated. Thereafter, the hydraulic pressure will force the bit against the bottom of the bore hole and as drilling proceeds, the extensible section 32 will extend after the mandrel 44 has extended some predetermined distance less than the total travel of the extensible section. Then the vertical drive means 18 should be slacked off until the drill string weight begins to appear again on the indicator 20 thus indicating that the extensible section 32 has again been retracted. Thereafter, the same sequence will be repeated with the hydraulic forcesforcing .the bit against the bottom of the bore hole and with the extensible section 32 extending as the drilling proceeds.

While only a few embodiments of this invention have been described in detail, those in the art will recognize that many modifications may be made in the exemplary embodiments without materially departing from the ad vantages of this invention.

What is claimed is:

l. A method for drilling a well bore hole using a drill string which includes an extensible unanchored hydraulic cylinder and piston section above a drill bit, said method comprising:

positioning said extensible section in a less than fully extended condition without anchoring any portion thereof to the bore hole, and

pumping pressurized fluid into said extensible section thereby producing hydraulic forces reacting against the drill string weight and tending to extend said extensible section thus influencing the effective force applied to said drill bit.

2. A method as in claim 1 wherein said positioning step comprises:

lowering said drill string into said bore hole until indicated drill string weight begins to decrease and then further lowering said drill string by a predetermined amount.

3. A method as in claim 1 further comprising the step of rotating said drill string simultaneously with said pumping step.

4. A method as in claim 1 further comprising the step of controlling the pressure of said pressurized fluid to achieve a substantially constant force between said drill bit and the bottom of said bore hole.

5. A method as in claim 1 wherein said positioning step comprises:

lowering said drill string into said bore hole to a first point until said extensible section is substantially retracted,

holding the upper portion of said drill string located above said extensible section at said first point while permitting the extensible section to extend, and cyclically repeating said lowering and holding steps.

6. A method as in claim 1 wherein said positioning and pumping steps comprise:

rotating said drill string while fluid pressure is applied to partially extend said extensible section, stopping the rotary motion,

slacking off said drill string to completely retract said extensible section, and then restarting said rotary motion without further slacking off said drill string.

7. A method as in claim 6 wherein said stopping, slacking and restarting steps are cyclically repeated.

8. A method for drilling a well bore hole using a drill string which includes an extensible hydraulic cylinder and piston section above a drill bit, said method comprising:

positioning said extensible section in a less than fully extended condition, and

pumping pressurized fluid into said extensible section thereby producing hydraulic forces tending to extend said extensible section and thus influence the effective force applied to said drill bit,

wherein said positioning and pumping steps comprise; pulling the bit free of the bottom of said bore hole,

slacking off said drill string until the bit touches the bottom of said bore hole and said extensible section is at least partially closed,

holding said drill string,

increasing the fluid pressure in said extensible section,

rotating said drill string, and then further slacking off said drill string until a desired drilling force is achieved.

9. A method for drilling a well bore hole using a drill string which includes an extensible hydraulic cylinder and piston section above a drill bit, said method comprising:

positioning said extensible section in a less than fully extended condition, and

pumping pressurized fluid into said extensible section thereby producing hydraulic forces tending to extend said extensible section and thus influence the effective force applied to said drill bit,

wherein said positioning and pumping steps comprise:

pulling the bit free of the bore hole bottom,

rotating said drill string with suflicient applied fluid pressure to fully extend said extensible section, and

tensible section. 

1. A method for drilling a well bore hole using a drill string which includes an extensible unanchored hydraulic cylinder and piston section above a drill bit, said method comprising: positioning said extensible section in a less than fully extended condition without anchoring any portion thereof to the bore hole, and pumping pressurized fluid into said extensible section thereby producing hydraulic forces reacting against the drill string weight and tending to extend said extensible section thus influencing the effective force applied to said drill bit.
 2. A method as in claim 1 wherein said positioning step comprises: lowering said drill string into said bore hole until indicated drill string weight begins to decrease and then further lowering said drill string by a predetermined amount.
 3. A method as in claim 1 further comprising the step of rotating said drill string simultaneously with said pumping step.
 4. A method as in claim 1 further comprising the step of controlling the pressure of said pressurized fluid to achieve a substantially constant force between said drill bit and the bottom of said bore hole.
 5. A method as in claim 1 wherein said positioning step comprises: lowering said drill string into said bore hole to a first point until said extensible section is substantially retracted, holding the upper portion of said drill string located above said extensible section at said first point while permitting the extensible section to extend, and cyclically repeating said lowering and holding steps.
 6. A method as in claim 1 wherein said positioning and pumping steps comprise: rotating said drill string while fluid pressure is applied to partially extend said extensible section, stopping the rotary motion, slacking off said drill string to completeLy retract said extensible section, and then restarting said rotary motion without further slacking off said drill string.
 7. A method as in claim 6 wherein said stopping, slacking and restarting steps are cyclically repeated.
 8. A method for drilling a well bore hole using a drill string which includes an extensible hydraulic cylinder and piston section above a drill bit, said method comprising: positioning said extensible section in a less than fully extended condition, and pumping pressurized fluid into said extensible section thereby producing hydraulic forces tending to extend said extensible section and thus influence the effective force applied to said drill bit, wherein said positioning and pumping steps comprise; pulling the bit free of the bottom of said bore hole, slacking off said drill string until the bit touches the bottom of said bore hole and said extensible section is at least partially closed, holding said drill string, increasing the fluid pressure in said extensible section, rotating said drill string, and then further slacking off said drill string until a desired drilling force is achieved.
 9. A method for drilling a well bore hole using a drill string which includes an extensible hydraulic cylinder and piston section above a drill bit, said method comprising: positioning said extensible section in a less than fully extended condition, and pumping pressurized fluid into said extensible section thereby producing hydraulic forces tending to extend said extensible section and thus influence the effective force applied to said drill bit, wherein said positioning and pumping steps comprise: pulling the bit free of the bore hole bottom, rotating said drill string with sufficient applied fluid pressure to fully extend said extensible section, and slacking off the drill string to partially close said extensible section. 